Heat oil in large skillet. Add hash browns, onion, and bell peppers. Cook until potatoes begin to brown.
Spray 9 x 13 baking dish with Pam. Spread potato mixture in pan. Top with ham. Pour beaten eggs mixture on top, making sure to coat all ingredients with eggs. Sprinkle with cheese. Cover and refrigerate overnight.
Bake uncovered at 375 for 45-55 minutes. Cover with foil near end, if browning too quickly.